Researchers doubt mammoths would ever have ventured up to the high, rocky plateau where Neanderthals were alleged to have chased them. Photograph: Getty

Heaps of mammoth and woolly rhino bones found piled up at the foot of a cliff were thought to be the grim results of Neanderthals driving the beasts over the edge.

The piles of bones are a major feature at La Cotte de St Brelade on Jersey, one of the most spectacular Neanderthal sites in Europe. But the claim that they mark the remains of mass slaughter has been all but ruled out by a fresh investigation.

Researchers have found that the plateau that ends at the cliff edge was so rocky and uneven that mammoths and other weighty beasts would never have ventured up there. Even if the creatures had clambered so high, the Neanderthals would have had to chase them down a steep dip and back up the other side long before the animals reached the cliff edge and plunged to their doom.

"I can't imagine a way in which Neanderthals would have been able to force mammoths down this slope and then up again before they even got to the edge of the headland," said Beccy Scott, an archaeologist at the British Museum. "And they're unlikely to have got up there in the first place."

Hundreds of thousands of stone tools and bone fragments have been uncovered at the Jersey site where Neanderthals lived on and off for around 200,000 years. The site was apparently abandoned from time to time when the climate cooled, forcing the Neanderthals back to warmer territory.

Scott and her colleagues drew on a survey of the seabed that stretches away from the cliff to reconstruct the landscape when the Neanderthals lived there. The land, now submerged under higher sea levels, was cut with granite ravines, gullies and dead-end valleys – a terrain perfect for stalking and ambushing prey.

"The site would have been an ideal vantage point for Neanderthal hunters. They could have looked out over the open plain and watched mammoths, woolly rhinos and horses moving around. They could see what was going on, and move out and ambush their prey," said Scott. Details of the study are published in the journal Antiquity.

The researchers have an alternative explanation for the bone heaps. Neanderthals living there may have brought the bones there after hunts, or from scavenged carcasses, and used them for food, heating and even building shelters. Older sediments at the site are rich with burnt bone and charcoal, suggesting the bones were used as fuel. The heaps of bones were preserved when Neanderthals last abandoned the site, and a fine dust of silt blew over and preserved the remains.

Archaeologists have investigated the site at La Cotte de St Brelade since the mid-19th century. More artefacts have been unearthed here than at all the other Neanderthal sites in the British Isles put together.

The exposed coastal site, one of the last resting places of the Neanderthals, was battered by fierce storms in February, raising fears that ancient remains at the site had been destroyed.